I went with the two 15s because they fit in the bed of my older truck with my ATV in the bed too.
My old TT had a 40 gallon FW tank and my EX went thru water like we had an endless supply of it. She never did understand "conserve".
But I fixed that problem.
I bleach mine in the spring and don't store them in the sun.
When I got these the local Primeland co-op had a few of them they had put nozzles on the bottom to sell..They didn't sell well so they made me an offer for all of them I couldn't refuse..
At the time I had a 30ft TT we spent months in at a time and putting 100 gallons in the pickup was not a big thing..I also have the two 25 gallon bottles I used,plummed into the front propane setup of the TT..
Now with a truck camper,I am always on the move never staying long anywhere so the water barrels hardly get used other than hunting season..One reason I went back to another truck camper was to drive and explore wherever I want without worry of turning around with a TT on a dead end road...
We use backcountry water filters(Sawyer) for fresh drinking water and coffee if we run low in the TC..